S-Contact for SOI

ABSTRACT

Systems, methods, and apparatus for an improved protection from charge injection into layers of a device using resistive structures are described. Such resistive structures, named s-contacts, can be made using simpler fabrication methods and less fabrication steps. In a case of metal-oxide-semiconductor (MOS) field effect transistors (FETs), s-contacts can be made with direct connection, or resistive connection, to all regions of the transistors, including the source region, the drain region and the gate.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of US application Ser. No.14/964,412 filed on Dec. 9, 2015, the disclosure of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

Various embodiments described herein relate generally to systems,methods, and apparatus for protection against charging of asilicon-on-insulator (SOI) device during a manufacturing phase of thedevice.

BACKGROUND

A fabrication phase of a semiconductor device can include a process thatsubjects the semiconductor device to a potential gradient, or induces acharge on the surface of the semiconductor device. In some cases, highenergy electrically charged particles (ions), associated with such aprocess can in turn enter layers of the semiconductor device and gettrapped inside such layers. Trapped charges inside the layers can inturn adversely affect operating characteristics of the semiconductordevice, such as high variation of corresponding threshold voltages, andin extreme cases can cause breakup of internal structures/layers of thedevice, rendering the device non-functional.

Various methods and apparatus for providing a discharge path for thecharges injected inside the various layers of the semiconductor deviceduring, for example, the plasma etching phase, have been devised. Suchsemiconductor devices can include metal-oxide-semiconductor (MOS) fieldeffect transistors (FETs), and particularly to MOSFETs fabricated onsilicon-on-insulator (SOI) and silicon-on-sapphire (SOS) substrates.

In particular, methods and apparatus for providing a discharge path tolayers of an SOI device fabricated on a low resistivity substrate use acombination of an active diode and/or a junction diode. Such diodes areused so as to not affect normal operation of the semiconductor devicefitted with the discharge path. In cases where a high resistivitysubstrate is used to fabricate the SOI device, it may be desirable toprovide a simpler, more compact, and yet effective discharge path.

SUMMARY

According to a first aspect of the present disclosure, a device ispresented, the device comprising: a high resistivity semiconductorsubstrate; an insulation layer overlying the substrate; an active layeroverlying the insulation layer and comprising active regions andisolation regions of the device; a transistor formed in an isolatedportion of the active layer, the transistor comprising a drain region, asource region and a gate channel region; and a first conductivestructure resistively connecting one of: a) a drain contact or a sourcecontact, and b) a gate contact to the semiconductor substrate, the firstconductive structure comprising: a first conductive line connecting theone of a) and b) to a first conductive contact, the first conductivecontact extending through the active layer at a region of the activelayer outside the isolated portion of the active layer, and through theinsulation layer to make contact with the semiconductor substrate.

According to a second aspect of the present disclosure, a device ispresented, the device comprising: a high resistivity semiconductorsubstrate; a trap rich layer overlying the substrate an insulation layeroverlying the trap rich layer; an active layer overlying the insulationlayer and comprising active regions and isolation regions of the device;a transistor formed in an isolated portion of the active layer, thetransistor comprising a drain region, a source region and a gate channelregion; and a first conductive structure resistively connecting one of:a) a drain contact or a source contact, and b) a gate contact to thesemiconductor substrate, the first conductive structure comprising: afirst conductive line connecting the one of a) and b) to a firstconductive contact, the first conductive contact extending through theactive layer at a region of the active layer outside the isolatedportion of the active layer, further extending through the insulationlayer and penetrating the trap rich layer to make resistive contact withthe semiconductor substrate.

According to third aspect of the present disclosure, a method forproviding a discharge path to a silicon-on-insulator (SOI) transistordevice is presented, the method comprising: (i) forming an active layeron a high resistivity substrate, the active layer being isolated fromthe high resistivity substrate via an insulation layer overlying thehigh resistivity substrate; (ii) forming active regions of thetransistor device within an isolated portion of the active layer, theactive regions comprising a source region, a drain region and a gatechannel region of the transistor device; (iii) forming a firstconductive structure resistively connecting at least one of: a) a draincontact and/or a source contact, and b) a gate contact of the transistordevice to the high resistivity substrate, the first conducting structurebeing formed by: forming a first conductive line connecting the at leastone of a) and b) to a first conductive contact; extending the firstconductive contact through the active layer at a region of the activelayer outside the isolated portion of the active layer, and through theinsulation layer to make a resistive contact with the high resistivitysemiconductor substrate, and (iv) based on the forming of the firstconductive structure, providing a first discharge path to the transistordevice.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more embodiments of thepresent disclosure and, together with the description of exampleembodiments, serve to explain the principles and implementations of thedisclosure.

FIG. 1 shows a semiconductor substrate placed inside a plasma etchingchamber.

FIG. 2A shows a top view of a silicon-on-insulator (SOI) transistordevice.

FIG. 2B shows a cross-sectional view of the silicon-on-insulator (SOI)transistor device of FIG. 2A along line AA of FIG. 2A. The SOItransistor device is shown comprising active regions formed in an activelayer and a gate polysilicon structure of a gate polysilicon layerfabricated atop an insulation layer.

FIG. 3A shows a prior art embodiment for providing discharge paths to anactive layer and a gate polysilicon layer of an SOI transistor device.

FIG. 3B shows a schematic representation of the prior art device of FIG.3A when the device is inside a process chamber.

FIG. 3C shows a schematic representation of the prior art device of FIG.3A during normal operation of the device.

FIG. 4A shows two s-contacts according to an embodiment of the presentdisclosure provided to an SOI transistor device. The s-contacts providedischarge paths to an active layer (source region) and a gatepolysilicon layer of the SOI transistor device.

FIG. 4B shows two s-contacts according to an embodiment of the presentdisclosure provided to an SOI transistor device. The s-contacts providedischarge paths to an active layer (drain region) and a gate polysiliconlayer of the SOI transistor device.

FIGS. 4C-4D show an SOI transistor device with one s-contact accordingto an embodiment of the present disclosure provided to one region of thetransistor device. Other regions of the transistor device can beresistively coupled to s-contacts provided to other transistor devices.

FIG. 4E shows two neighboring transistor devices, each with ones-contact according to an embodiment of the present disclosure.

FIG. 4F shows a resistive coupling of an s-contact, associated with afirst transistor device, to a second transistor device according to anembodiment of the present disclosure.

FIGS. 4G-4H show two s-contacts according to an embodiment of thepresent disclosure provided to an SOI transistor device, where thes-contacts penetrate through active regions of the transistor device.

FIG. 4I shows two s-contacts according to an embodiment of the presentdisclosure provided to an SOI transistor comprising a trap rich layer.

FIG. 4J shows a schematic representation of the device of FIG. 4A whenthe device is inside a process chamber.

FIG. 4K shows a schematic representation of the device of FIG. 4A duringnormal operation of the device.

FIG. 4L shows a schematic representation of the device of FIG. 4B whenthe device is inside a process chamber.

FIG. 4M shows a schematic representation of the device of FIG. 4B duringnormal operation of the device.

FIGS. 5A-5B show a top view of an SOI transistor device fitted with aplurality of s-contacts according to the present invention.

DETAILED DESCRIPTION

Throughout this description, embodiments and variations are describedfor the purpose of illustrating uses and implementations of theinventive concept. The illustrative description should be understood aspresenting examples of the inventive concept, rather than as limitingthe scope of the concept as disclosed herein.

Apparatus and methods that provide a discharge path from layers of asemiconductor device fabricated atop an insulation (electricallyinsulating) layer are described in the present disclosure. The dischargepaths according to the various embodiments of the present disclosure arepurely resistive paths and are therefore simpler in construction andcomprise fewer fabrication steps when compared to prior art embodiments.Such purely resistive discharge paths can be provided to semiconductordevices which comprise an active layer isolated from an underlying highresistivity substrate via an insulation layer. An exemplary suchsemiconductor device is an SOI MOSFET transistor (e.g. 400A of FIG. 4Alater described) which comprises an insulation buried oxide layer (BOX)(102) between the active layer (103) of the transistor and the highresistivity substrate (401), where the active layer (103) comprisesdrain (206) and source (207) regions of the transistor surrounding agate channel (210) of the transistor. In some embodiments the gatechannel (210) is defined by a corresponding gate polysilicon structure(204), which is part of a gate polysilicon layer.

As used herein, the expression “active layer” is used to indicate thelayer (e.g. 103) which overlies the buried oxide layer (BOX) (e.g. 102)and which is obtained via various CMOS processing steps starting from anoriginal silicon layer. The active layer can include active regions(e.g. 206, 207, 210, 219) of active devices, as well as isolationregions (e.g. 208). In some embodiments, the isolation regions can beused to isolate neighboring active regions of the active layer. In someembodiments the active layer can include passive components, such asresistors, created within regions of the active layer. In general,regions of the active layer where current flows can be referred to asactive regions of the active layer.

As used herein, the expression “gate polysilicon layer” is used toindicate a layer (e.g. 104 of FIG. 1) in which gate polysiliconstructures (e.g. 204 of FIG. 2B) defining gate channels (e.g. 210 ofFIG. 2B) of different semiconductor devices are formed. The gatepolysilicon layer can include contiguous and non-contiguous gatepolysilicon structures associated with the different semiconductordevices.

The s-contacts according to the present disclosure can provide resistivedischarge paths to the active layer and to the gate polysilicon layer byresistively connecting regions of such layers, such as active regions ofthe active layer and gate polysilicon structures of the gate polysiliconlayer, to the high resistivity semiconductor substrate upon which thelayers are fabricated.

As used herein, an s-contact in a semiconductor device, as per thevarious embodiments of the present disclosure, is a resistive path (e.g.combination of (315, 316, 317) or (325, 326, 327) of FIGS. 4A-4B) whichprovides a resistive conduction path between a contact point at asurface of a layer (e.g. regions 206, 207 of layer 103 or region 204 oflayer 104 as depicted in FIGS. 4A-4B) of the semiconductor device and acontact point at a surface of a high resistivity substrate (e.g. 401 ofFIGS. 4A-4B) of the semiconductor device. A person skilled in the artwill know of many fabrication methods to provide an s-contact accordingto the present disclosure.

According to the various embodiments of the present disclosure, materialused for the s-contact can be any low resistivity conductive material,such as polysilicon and various metals (e.g. tungsten, copper, etc.).The s-contact according to the present disclosure can be of a samematerial or comprising several materials providing a piece-wiseconstruction of the s-contact (e.g. (315, 316, 317) or (325, 326, 327)of FIGS. 4A-4B).

According to an embodiment of the present disclosure, the s-contactpenetrates through an isolation region (e.g. 208 of FIG. 4A) of theactive layer (e.g. 103 of FIG. 4A) of the semiconductor device, andpenetrates through the insulation layer (e.g. BOX layer 102 of FIG. 4A)of the semiconductor device to reach, and make contact with, the highresistivity substrate (e.g. 401 of FIG. 4A). In a case of an SOI device,the isolation region (208) can be a shallow trench isolation (STI)region. It should be noted that by virtue of penetrating through theisolation region (208) of the active layer (103), the s-contact remainsisolated from the active regions (e.g. 206, 207, 210 of FIG. 4A) of thesemiconductor device at all points except for the contact points locatedat the surface of a layer (e.g. layer 103 or layer 104).

According to a further embodiment of the present disclosure, thes-contact penetrates through the active layer (e.g. 103 of FIG. 4A-4I)of the semiconductor device at an active region (e.g. 219 of FIGS.4A-4I) of the active layer which can be isolated from other activeregions (e.g. 206, 207, 210 of FIGS. 4A-4I) of the device, andpenetrates through the insulation layer (e.g. BOX layer 102 of FIGS.4A-4I) of the semiconductor device to reach, and make contact with, thehigh resistivity substrate (e.g. 401 of FIGS. 4A-4I). Isolation of theactive regions (206, 207, 210) inside the active layer (103) can beprovided via isolation regions (e.g. 208 of FIGS. 4A-4I, which can beSTI regions).

According to a further embodiment of the present disclosure a pluralityof s-contacts (e.g. (315, 316, 317) and (325, 326, 327) of FIGS. 4A-4B)can be provided for a same semiconductor device. Such plurality ofs-contacts can be provided to active regions of the semiconductor deviceformed in the active layer (103), including a drain region (206) and/ora source region (207) of the device, and to the gate polysiliconstructure (204) of the device formed in the gate polysilicon layer(104).

According to a further embodiment of the present disclosure, a pluralityof devices are formed on a high resistivity substrate (401), and aplurality of s-contacts are provided to active regions of the activelayer and to gate polysilicon structures of the gate polysilicon layerassociated with the plurality of devices.

According to a further embodiment of the present disclosure, ans-contact making a direct connection to a first device can also providea discharge path to other devices which are resistively coupled to thefirst device. The first and the other devices can be, for example, partof a circuit, and interconnections of such a circuit can provideresistive coupling between one or more active regions/gate polysiliconstructures of the other devices and an active region/gate polysiliconstructure of the first device which is directly connected to ans-contact, thereby effectively providing a resistive discharge path tothe one or more active regions/gate polysilicon structures of the otherdevices. Accordingly, a circuit comprising a plurality of devices (e.g.transistors) can be protected by a shared number of s-contacts, wherethe sharing is provided via resistive interconnections of the pluralityof devices. This can effectively protect all the active regions and allthe gate polysilicon structures of the plurality of the devices. Inother words, any active region and gate polysilicon structure of atransistor device of the circuit has either a direct connection to ans-contact, or is resistively coupled to an s-contact via circuitinterconnections. With reference to FIG. 4A, the conductive contact(316) of the s-contact (315, 316, 317) makes a direct connection to theactive region (207) of the device (400A). In other words, the activeregion (207) of device 400A has a direct connection to the s-contact(315, 316, 317), and the s-contact is said to be associated with thedevice (400A).

According to a further embodiment of the present disclosure thes-contact makes contact to a region (e.g. 204, 206, 207) of thesemiconductor device via a first conductive contact (e.g. 316 and 326 ofFIG. 4A), and makes contact to the high resistivity substrate (401) viaa second conductive contact (e.g. 315 and 325 of FIG. 4A), where thefirst and the second conductive contacts are conductively joined via aconductive line (e.g. 317 and 327 of FIG. 4A). According to anembodiment of the present disclosure the conductive line is part of ametal layer of the semiconductor device.

According to a further embodiment of the present disclosure, a trap richlayer (e.g. 402 of FIG. 4I) can be provided between the high-resistivitysubstrate (401) and the BOX layer (102). A person skilled in the artreadily understands some of the benefits provided by including a traprich layer in an SOI device, description of which is outside the scopeof the present disclosure. In a case where a trap rich layer isprovided, the s-contact (e.g. 325, 326, 327 of FIG. 4I) can furtherpenetrate through the trap rich layer (402) to make (direct) contactwith the high resistivity substrate (401), or, the s-contact (e.g. 315,316, 317) can penetrate the trap rich layer (402) deep enough to make aresistive contact, through a remaining portion of the trap rich layer'sthickness, with the high resistivity substrate (401).

As used herein, a high resistivity substrate is a substrate with aresistivity in a range of 3,000 to 20,000 or higher ohm-cm. Theresistivity of the substrate can be controlled via the doping of thesubstrate, where a lighter doping provides a higher resistivity of thesubstrate. As known to a person skilled in the art, standard SOI processuses substrates with a low resistivity, below 1,000 ohm-cm. Given thesmall cross section (e.g. 0.35 μm×0.35 μm) of the conductive contact(315, 325) making contact to the high resistivity substrate (401), theeffective contact resistance between the conductive contact (315, 325)and the high resistivity substrate (401) is in the range of 0.2 to 20G-ohm due to distributed resistance as current crowds to the smallcontact, and to the non-ohmic nature of the interface due to the lightdoping of the substrate (401).

As presented in the following sections of the present disclosure, ans-contact according to the various embodiments of the present disclosurecan be provided by connecting two conductive contacts via a conductiveline, where a first conductive contact is connected to an active layeror a gate polysilicon layer of a semiconductor device and a secondconductive contact is connected to a high resistivity substrate of thesemiconductor device by penetrating through an insulation layer, andoptionally through a trap rich layer, of the semiconductor device.Furthermore, the s-contact can in turn be resistively coupled to anactive layer or a gate polysilicon layer of a different semiconductordevice via resistive interconnections of a common circuit. As discussedabove, connection to the active layer and to the gate polysilicon layercan be made via conductive contacts connected to active regions of theactive layer and to the gate polysilicon structure of the gatepolysilicon layer respectively.

The embodiments as described herein are exemplified by an N-type MOSFETdevice. A person of ordinary skill in the art will readily apply theinventive concepts as disclosed herein to other types of semiconductordevices, such as a P-type MOSFET device, by applying different types ofdoping schemes as appropriate. The embodiments according to the presentinvention can also be applied to extended drain devices, such aslaterally diffused metal oxide semiconductor (LDMOS) devices, and othergated transistors or devices which comprise an insulation layer betweenan active layer and a high resistivity substrate.

Semiconductor devices with s-contacts according to the variousembodiments of the present disclosure may include semiconductor devicesformed on silicon-on-insulators (SOI), including field effecttransistors (FET). The FET devices may include complementarymetal-oxide-semiconductor (CMOS), metal-oxide-semiconductor field-effecttransistor (MOSFET), and other type field-effect transistor (FET)devices.

In one exemplary embodiment according to the present disclosure, ans-contact can comprise a conductive contact in a square or rectangularshape. As will be described in later sections of the present disclosure,the s-contact can provide a low resistivity conduction path between aregion of a top layer of the semiconductor device to thehigh-resistivity substrate, and therefore provide a discharge path forinjected charges during a manufacturing process.

For an exemplary embodiment of an SOI MOSFET transistor according to thepresent disclosure, one or more s-contacts can be provided to a sourceand/or drain region of the transistor. Alternatively, or additionally,one or more s-contacts can be provided to the gate polysilicon structureof the transistor.

For an exemplary embodiment of a circuit comprising a plurality ofinterconnected SOI MOSFET transistors with corresponding active regionsand gate polysilicon structures, one or more s-contacts can be providedto the active regions of some or all of the transistors of the circuit,and one or more s-contacts can be provided to the gate polysiliconstructures of some or all of the transistors of the circuit. In oneexemplary embodiment, circuit interconnections can provide a resistivecoupling from an active region and/or gate polysilicon structure of afirst transistor to an s-contact of a second transistor, and thereforeprovide a discharge path to the first transistor.

According to a further embodiment of the present disclosure, number ofs-contacts and corresponding spatial placements in a semiconductordevice can be provided such as to limit a potential across any twopoints of the semiconductor device during a charge injection process(e.g. plasma etching). Given a known high resistivity value of thesubstrate and induced currents through the s-contacts during the chargeinjection process, the number of s-contacts to limit such potentialdifference can be derived. This can be performed with the help ofsimulation software. The person skilled in the art will understand thatdue to the purely resistive nature of the s-contacts according to thepresent invention, a trade off exists between a leakage during operationof the semiconductor device associated with the addition of thes-contacts, and the amount of protection the s-contacts provide duringmanufacturing of the device.

FIG. 1 shows a semiconductor substrate (101) placed inside an exemplaryhigh energy manufacturing process chamber (100). The semiconductorsubstrate (101) comprises an active silicon layer (103) comprisingactive regions of active components with corresponding conductivecontacts, and a (gate) polysilicon layer (104) comprising gatepolysilicon structures with corresponding conductive contacts atop thepolysilicon layer (104). The active layer (103) overlies an insulationlayer (102) which prevents conduction between the active layer (103) andthe substrate (101). The substrate (101) is placed on a bottom electrode(160) of the chamber which is connected to a bottom potential (190). Atop electrode (150) of the chamber is connected to a variable supply(180). Within the exemplary process chamber (100), the semiconductorsubstrate (101) can be subjected to an event which can create apotential gradient or induce charge on the semiconductor substrate(101), thus resulting in injected charges remaining trapped within thelayers (103), (104), or at interfaces between such layers, and cancreate large potential differences between such layers and the substrate(101) during a processing phase of the substrate. Trapped charges insidethe layers can adversely affect operating characteristics (for examplechange in threshold voltage, change leakage characteristics, etc.) ofthe active components, while the large potential differences between thelayers and the substrate can potentially damage the active components ofthe active layer rendering them non-functional. By providing a dischargepath via contacts at the surface of semi-conductive layers (103) and(104) to the bottom potential (190) coupled to the bottom electrode(160), injected charges into such semi-conductive layers can beprevented (e.g. removed).

FIG. 2A shows a top view of an N-type SOI MOSFET device (200) which canbe part of the active components formed in an active layer overlying thesemiconductor substrate (101). A gate finger (204) of the device (200)is shown to be located between a source region (207) and a drain region(206). The gate finger (204) has a length of L_(G) and a width of W_(G).In one aspect, the gate finger can be made via a gate polysiliconstructure (204), formed within the polysilicon layer (104), which canblock implantation of dopant ions used to dope the neighboring sourceand drain regions of the MOSFET. A person of ordinary skill in the artreadily knows that a multi-finger SOI device can have a plurality ofsuch fingers electrically coupled, where each finger can comprise acorresponding gate polysilicon structure (204) with corresponding gatecontacts (213), a drain region (206) with corresponding drain contacts(212) and a source region (207) with corresponding source contacts(211). In some embodiments, neighboring fingers can share acorresponding drain and/or source region. Alternatively, a plurality offingers corresponding to a plurality of transistor devices can share asame common semiconductor substrate (101) and be electrically isolatedwith respect to one another. Isolation of the active regions (206, 207)of the device (200) with respect to other active regions (219) formed onthe semiconductor substrate (101) can be provided via isolation regions(208). The person of ordinary skills will know that regions outside thelabelled regions of FIG. 2A can comprise active regions (219) orisolation regions (208).

FIG. 2B shows a cross sectional view of the N-type SOI MOSFET device(200) along line AA of FIG. 2A. As shown in the cross sectional view ofFIG. 2B, the SOI MOSFET comprises a layered structure, formed atop thesubstrate (101), comprising layers (102), (103), (204) and (205). In oneaspect, the layer (204), which forms the gate polysilicon structure ofthe device, is shown to be laid over an insulating gate silicon oxidelayer (205). In one aspect, the body region (210) under the layer (204)is doped with a P-type dopant (P-body), and the source (207) and drain(206) regions are heavily implanted with an N-type dopant (N+). As shownin the figures, regions (206), (207) and (210) are part of an activelayer (103) which is laid over an insulting buried oxide (BOX) layer(103). Furthermore, as shown in FIGS. 2A and 2B, the device (200) isshown to be isolated from adjacent regions within the active layer (103)(which may contain neighboring circuits comprising otherfingers/transistors, not shown) by way of shallow trench isolation (STI)regions (208) which are of non-conductive types. Due to the insulatingnature of the BOX layer (102), a conduction path between layers (103),(204) and (205) and the semiconductor substrate (101) is not provided inthe SOI MOSFET depicted in FIGS. 2A and 2B, and therefore device (200)is susceptible to charge injection during a high potential manufacturingprocess.

FIG. 3A shows a prior art embodiment of an SOI MOSFET device (300) whichprovides a first discharge path between a contact (326) on the gatepolysilicon structure (204) and the semiconductor substrate (101), and asecond discharge path between a contact (316) on the source region (207)of the device (300) and the semiconductor substrate (101). The personskilled in the art will realize that FIG. 3A does not show an exactcross section of an SOI MOSFET as contact (326) to the gate polysiliconstructure (204) is typically in a different cross sectional plane fromthe cross section plane of contact (316) to the source region (207).

As can be seen in the prior art embodiment depicted in FIG. 3A, thefirst discharge path comprising the conductive contact (326), conductiveline (327), conductive contact (325), N-type doped region (345), and thesemiconductor substrate (101). Conductive contacts (325, 326) andconductive line (327) can be made of metal, such as copper or tungsten.Furthermore, the N-type doped region (345), buried within thesemiconductor substrate (101), and the P-type doped region of thesubstrate (101), making contact to the region (345), create a junctiondiode. Therefore, the first discharge path couples the gate polysiliconlayer (204) to the semiconductor substrate (101) via a junction diode.

The second discharge path of the prior art device (300) depicted in FIG.3A comprises the conductive contact (316), conductive line (317),conductive contact (315), P-type doped region (340), and thesemiconductor substrate (101). Similar to the first discharge path,conductive contacts (315, 316) and conductive line (317) can be made ofmetal, such as copper or tungsten.

It should be noted that both the first and the second discharge paths ofthe prior art device (300) couple the conductive contacts (315) and(325) to the semiconductor substrate (101) via regions (340) and (345)respectively. Therefore direct contact between such contacts and thesemiconductor substrate (101) is not present in the prior art embodimentdepicted in FIG. 3A.

When the prior art device (300) is placed in the process chamber (100),the junction diode formed by elements (345) and (101) of the firstdischarge path allows for a flow of charge (e.g. electrons) from thegate polysilicon structure (204) of the polysilicon layer (104) to thebottom electrode plate to which the semiconductor substrate (101) iscoupled. Similarly, the second discharge path allows for a flow ofcharge from the source region (207) of the active layer (103) to thebottom electrode plate to which the semiconductor substrate (101) iscoupled. The person skilled in the art will realize that the junctiondiode can be leaky for the currents generated inside of the processchamber, and therefore charges can flow in either direction.

In the prior art device (300) depicted in FIG. 3A, the semiconductorsubstrate (101) has a low resistivity, and can therefore provide a lowresistance conduction path between any two regions inside the substrate(101), including regions (340) and (345). Therefore, the junction diodeformed by regions (345, (101) of the prior art device (300) is requiredsuch as to not allow a conduction path between the gate contact (326)and the source contact (316) during normal operation of the device (e.g.via a low resistivity path provided by the semiconductor substrate (101)between conductive contacts (315) and (325)).

FIGS. 3B and 3C schematically represent the prior art device (300) inthe configuration (300B), where the device is inside the process chamber(100), and in the configuration (300C), where the device is duringnormal operation. These figures show the transistor device (300) and thecorresponding conduction paths for each of the two configurations (300B)and (300C). Resistor δR₂ represents the combined (low) resistance of(325, 326, 327), resistor δR₁ represents the combined (low) resistanceof (315, 316, 317), item (375) represents the junction diode formed by(345) and adjacent regions of (101), δr₀ represents a resistance of alow resistivity path between region (340) and region (345) of the device(300), and (δr₁, δr₂) represent resistances of low resistivity pathsbetween each of the regions (340, 345) and the bottom electrode of theprocess chamber (which is provided a low reference potential, such asground). The person skilled in the art will understand that resistances(δr₀, δr₁, δr₂) are provided by the low resistivity semiconductorsubstrate (101).

With further reference to FIG. 3C, as described above, due to the lowresistivity nature of the substrate (101) of the prior art embodimentdevice (300), the diode (375) is required so as to not provide a currentloading of the gate by the source. The person skilled in the art willnotice that the required diode (375) blocks a current flow between thegate (G) and the source (S) of the device only during operation of thetransistor device (300) where the gate voltage V_(G) is higher than thesource voltage V_(S), which thereby puts the diode (375) in a reversebias condition. The prior art embodiment therefore assumes that duringnormal operation of the device (300), the gate voltage is not lower thanthe source voltage, as such a condition puts the diode (375) in aforward bias condition, and prevents a desired negative biasing(V_(G)<V_(S)) of the device.

FIG. 4A shows an exemplary embodiment according to the presentdisclosure of an SOI MOSFET device (400A) provided with s-contacts. Afirst s-contact (326, 327, 325) provides a first discharge path betweena contact (326) on the gate polysilicon structure (204) formed in thepolysilicon layer (104) and the semiconductor substrate (401), and asecond s-contact (316, 317, 315) provides a second discharge pathbetween a contact (316) on the source region (207) formed in the activeregion (103) of the device (400A) and the semiconductor substrate (401).By using a high resistivity semiconductor substrate (401), thes-contacts, and therefore the first and the second discharge paths ofthe device (400A) according to the present invention, can be made devoidof an active device (e.g. the diode (375) described in relation to theprior art embodiment depicted in FIGS. 3A-3C described above) and canremain purely resistive. As a consequence, efficacy of protection duringa high energy process can be maintained with simpler structures andfewer fabrication steps of the device according to the presentinvention.

As can be seen in the embodiment according to present disclosuredepicted in FIG. 4A, the first discharge path (s-contact) comprises aconductive contact (326) making contact with the gate polysiliconstructure (204), a conductive line (327), and a conductive contact (325)which makes direct contact with the semiconductor substrate (401)(contrary to the prior art embodiment depicted in FIG. 3A, where contactis indirect and through a coupling region (345) which creates a junctiondiode). Similarly, the second discharge path (s-contact) comprises aconductive contact (316) which makes contact with the source region(207), a conductive line (317), and a conductive contact (315) whichmakes direct contact with the semiconductor substrate (401). In anexemplary embodiment of the present disclosure, conductive contacts(315, 316, 325, 326) and conductive lines (317, 327) can be made ofmetal, such as copper or tungsten. In alternative embodiments accordingto the present disclosure, such contacts can be made of any lowresistivity conductive material, including other metals and polysilicon.

According to further embodiments of the present disclosure, thes-contacts can be resistively coupled to regions (e.g. source, drain,gate polysilicon) of other devices, thereby effectively providing suchregions with discharge paths for injected charges.

With further reference to FIG. 4A, the person skilled in the art readilyrealizes that both the first and the second discharge paths (s-contacts)according to the present disclosure are purely resistive paths andtherefore can allow symmetrical flow of charges from the two ends of thepaths. This means that the present invention provides discharge pathsfor injected charges irrespective of a polarity of the potentialgradient provided by sources (180, 190) of FIG. 1. Furthermore,decoupling of the discharge paths (and therefore between the source andthe gate of the device) during normal operation of the device isprovided by the high resistivity nature of the semiconductor substrate(401) which provides a high resistance path between the contact (315)and the contact (325). This means that contrary to the prior artembodiment depicted in FIGS. 3A-3C, the present invention allows, duringnormal operation of the device, for any biasing of the gate with respectto the source of the device, including a negative biasing (V_(G)<V_(S))of the device according to the present invention. The person skilled inthe art will appreciate such flexibility, as a negative biasing canprovide, for example, a higher input/output isolation in some RFswitching implementations.

According to further embodiment of the present disclosure, the seconddischarge path can be provided to the drain region of the transistordevice instead of the source region, as depicted in FIG. 4B, with samelevel of decoupling (via high resistivity path) of the two paths asdescribed above.

According to further embodiments of the present disclosure, separate andcoexisting s-contacts (discharge paths) to each of the source region(207), drain region (206) and the gate polysilicon structure (204) canbe provided. This embodiment represents a combination of the embodimentrepresented by FIGS. 4A and 4B. FIGS. 5A and 5B, later described, showsuch combination.

A semiconductor device according to the present invention can beprovided with one, two, or more s-contacts, each with a directconnection to the drain/source region and/or gate polysilicon structureof the device. FIGS. 4A-4B show semiconductor devices according to thepresent disclosure having s-contacts each directly connected (directconnection) to the drain/source region and to the gate polysiliconstructure of the device. FIGS. 4C-4D show a semiconductor device (400C,400D) according to the present disclosure having an s-contact, (325,326, 327), (315, 316, 317), directly connected to either the gatepolysilicon structure (204) (FIG. 4C), or to the drain/source region(206/207) (FIG. 4D) of the device. As described above, although thesemiconductor device (400C, 400D) does not include a direct connectionto an s-contact for both an active region (e.g. 206, 207) of the deviceand the gate polysilicon structure of the device, a resistive coupling(connection) to an s-contact which has a direct connection to adifferent semiconductor device can be provided to the semiconductordevice (400C, 400D).

FIG. 4E shows an exemplary configuration of the two semiconductordevices (400C, 400D) of FIGS. 4C and 4D fabricated on a same highresistivity semiconductor substrate (401). As can be seen in FIG. 4E,each of the s-contacts (325, 326, 327) and (315, 316, 317) penetratethrough the layer (103) at an isolation region (208) of the layer, whichisolates the active regions (e.g. 205, 206, 207) of the twosemiconductor devices. In the exemplary embodiment according to thepresent disclosure depicted in FIG. 4E, the two s-contacts are shown topenetrate through a same (contiguous) isolation region (208). The personskilled in the art will know not to consider such exemplary embodimentas limiting what the inventors consider to be their invention, as, forexample, the isolation region (208) need not be a contiguous region, andeach of the s-contacts can penetrate through a different andnon-contiguous isolation region.

According to a further exemplary embodiment of the present disclosure,the s-contacts associated with two different semiconductor devices(400C, 400D) can penetrate the layer (103) at distinct (non-contiguous)isolation regions (208), as depicted in FIG. 4F. The exemplaryembodiment according to the present disclosure depicted in FIG. 4F showsone exemplary configuration for resistively coupling (e.g. via elements425, 426, 427, 219, 415, 417) an active region (206) of a first device(400C) to an s-contact (315, 316, 317) which is directly connected to anactive region of a second device (400D), the first and the seconddevices having their respective active regions (206, 207, 210) separatedby isolation regions (208).

As can be seen in the exemplary embodiment depicted in FIG. 4F, thedrain region (206) of the device (400C) is connected, via conductivecontact (425), conductive line (427) and conductive contact (426), to anactive region (219) formed inside the layer (103). The active region(219) in turn provides a resistive conduction path between theconductive contact (426) and a conductive contact (415). Finally, theconductive contact (415) is resistively coupled to the conductivecontact (315) of the s-contact (315, 316, 317) via conductive line(417), thereby providing the resistive coupling between the sourceregion (206) of the first device (400C) and the s-contact (315, 316,317) of the second device (400D).

With further reference to FIG. 4F, the active region (219), although notshown for clarity reasons, can include any active or passive componentwhich can provide a resistive conduction path between the two contacts(426) and (415). This can include, for example, a combination of one ormore resistors, one or more transistors, and related interconnections,that in combination, provide a resistive conduction path (thereforesymmetrical with respect to a current flow) between the two conductivecontacts (426) and (415), and thereby resistively couple an activeregion (206) of a first device (400C) to an s-contact which is directlyconnected to an active region (207) of a second device (400D). A personskilled in the art will understand that a similar configuration can beprovided for resistively coupling a gate polysilicon region of a firstdevice to an s-contact which is directly connected to a region (e.g.gate polysilicon structure) of a second device, the two devices beingseparated via one or more isolation regions (208).

In the various exemplary embodiments according to the present disclosurepresented above, the s-contact penetrates the layer (103) at anisolation region (208) formed in the layer (103). According to furtherexemplary embodiments of the present disclosure the s-contact canpenetrate at active regions of the layer (103) (e.g. regions of theactive layer (103) where current can flow), which can include drain andsource regions of a transistor device, as well as passive componentsformed in the layer (103), such as resistors. FIGS. 4G and 4H showexemplary embodiments according to the present disclosure where thes-contact penetrate the layer (103) at active regions (219) of the layerdifferent from the isolation regions (208). Similar embodiments based oneach of FIGS. 4C-4F can be provided, where the s-contacts penetrate anactive region (219) of the layer (103) instead of an isolation region(208) of the layer (103).

FIG. 4I shows a semiconductor device (400I) according to an embodimentof the present disclosure which is fabricated on a high resistivitysemiconductor substrate (401) with an overlying trap rich layer (402).As can be seen on FIG. 4I, the trap rich layer (402) is placed betweenthe high resistivity substrate (401) and the BOX layer (102). In a casewhere a trap rich layer is provided, the s-contact (e.g. 325, 326, 327of FIG. 4I) can further penetrate through the trap rich layer (402) tomake (direct) contact with the high resistivity substrate (401). This isdepicted in FIG. 4I, where it is shown that the conductive contact (325)of the s-contact (325, 326, 327) penetrates though the entire thicknessof the trap rich layer (402) to reach, and make contact with, the highresistivity semiconductor substrate (401). Alternatively, since the traprich layer can be conductive, the s-contact (e.g. 315, 316, 317 of FIG.4H) can penetrate the trap rich layer (402) deep enough to makeresistive contact, through a remaining thickness portion of the traprich layer, with the highly resistive substrate (401). This can be seenin FIG. 4I, where the conductive contact (315) of the s-contact (315,316, 317) penetrates the trap rich layer (402) at a depth ε, and doesnot make a direct contact with the high resistivity semiconductorsubstrate (401). The depth ε at which the conductive contact (315)penetrates the trap rich layer (402) is enough to provide a resistivecoupling (contact), of a desired resistance, through the remaining depthof the trap rich layer (402), to the high resistivity semiconductorsubstrate (401). In some embodiments, a depth ε substantially equal tozero can be sufficient to provide a desired resistive contact. Theperson skilled in the art will realize that any of the variousembodiments of the s-contact described above and with reference to FIGS.4A-4H can be also provided for the case where a trap rich layer isprovided between the high resistivity substrate (401) and the BOX layer(102) as depicted in FIG. 4I. It should be noted that the resistivity ofthe trap rich layer (402) is generally of a same order of magnitude asthe resistivity of the substrate (401).

FIGS. 4J and 4K schematically represent the device (400A) of the presentinvention in the configuration (400J), where the device is inside theprocess chamber (100), and in the configuration (400K), where the deviceis during normal operation. These figures show the transistor device(400A) and the corresponding conduction paths for each of the twoconfigurations (400J) and (400K) provided by the associated s-contacts.Resistor δR₂ represents the combined (low) resistance of the s-contact(325, 326, 327), resistor δR₁ represents the combined (low) resistanceof the s-contact (315, 316, 317), resistor r₀ represents a resistance ofa high resistivity path between contacts (315) and (325), and resistors(r₁, r₂) represent resistances of resistive conduction paths betweeneach of the contacts (315, 325) and the bottom electrode of the processchamber (which is provided a low reference potential, such as ground).The person skilled in the art will understand that resistances (r₀, r₁,r₂) are provided by the high resistivity semiconductor substrate (101).

FIGS. 4L and 4M schematically represent the device (400B) of the presentinvention in the configuration (400L), where the device is inside theprocess chamber (100), and in the configuration (400M), where the deviceis during normal operation. These figures show the transistor device(400B) and the corresponding conduction paths for each of the twoconfigurations (400L) and (400M) provided by the associated s-contacts.Resistor δR₂ represents the combined (low) resistance of the s-contact(325, 326, 327), resistor δR₁ represents the combined (low) resistanceof the s-contact (315, 316, 317), resistor r₀ represents a resistance ofa high resistivity path between contacts (315) and (325), and resistors(r₁, r₂) represent resistances of resistive conduction paths betweeneach of the contacts (315, 325) and the bottom electrode of the processchamber (which is provided a low reference potential, such as ground).The person skilled in the art will understand that resistances (r₀, r₁,r₂) are provided by the high resistivity semiconductor substrate (101).

According to a further embodiment of the present disclosure, the numberof s-contacts provided to a transistor device (e.g. 400A, 400B) can bein accordance to a desired high limit potential across any two points ofthe transistor device during the charge injection process (e.g. plasmaetching). Simulation software can provide such number and placement ofthe s-contacts in the device based on the high resistivity value of thesemiconductor substrate (401) and induced currents through thes-contacts during the charge injection process. For example, a desiredsmaller voltage drop across the semiconductor substrate (401) during thecharge injection process can be provided by an increased number ofs-contacts which can thereby reduce the effective (equivalent)resistance values of r₁ and r₂ of FIGS. 4C-4F. Furthermore, the distancebetween contacts (315) and (325) can be optimized so as to obtain,during normal operation of the device, a desired resistive isolationbetween the first and the second s-contacts, and therefore effectivelyadjust the resistance value of resistor r₀ of FIGS. 4J-4M (e.g.effective/equivalent resistance value between gate and source and/orbetween gate and drain to be larger than a specified minimum value).

FIG. 5A shows a simplified top view of an SOI transistor device (e.g.400A, 400B, 400I of FIGS. 4A, 4B, 4I) fitted with a plurality ofs-contacts (510) according to the present invention. In the exemplaryembodiment according to the present disclosure depicted in the FIG. 5A,two s-contacts (510) are provided to each of the source region (207),the drain region (206) and the gate polysilicon structure (204). As canbe seen in FIG. 5A, the s-contacts (510) can share contacts (211, 212,213) of the corresponding regions (source, drain, gate) and provide aresistive conduction path to the high resistivity semiconductorsubstrate (401) via conductive lines (317, 327) of the s-contacts goingabove and across the active regions (206, 207) of the device andreaching above the isolation regions (e.g. (208), where the conductivelines (317, 327) make contact with the conductive contacts (315, 325).In turn, the conductive contacts (315, 325) penetrate through theisolation regions (208) and the insulation layer (BOX) (102) to reachthe high resistivity semiconductor substrate (401) and make directcontact with the high resistivity semiconductor substrate (401). In acase where a trap rich layer (e.g. 402 of FIG. 4I) exists between thehigh resistivity semiconductor substrate (401) and the BOX layer (102),the conductive contacts (315, 325) also penetrate the trap rich layer,either fully, to make direct contact with the substrate (401), orpartially, to provide a resistive coupling to the substrate (401).

FIG. 5B shows a simplified top view of an SOI transistor device (e.g.400G, 400H of FIGS. 4G-4H) fitted with a plurality of s-contacts (510)according to the present invention. In contrast to the exemplaryembodiment according to the present disclosure depicted in FIG. 5A, thes-contacts of the SOI device depicted in FIG. 5B can penetrate a toplayer of the device, which contains active regions (206, 207) of thedevice, via conductive contacts (315, 325), at an active region (219)which is isolated, via isolation regions (208), from the active regions(206, 207) of the device. The isolated region (219) can be an activeregion of a separate transistor, a resistor or any other device.Alternatively, one or more of the contacts (315, 325) do not penetratethe active region (219), but rather make resistive contact to the activeregion (219), the active region being in turn resistively coupled to thesemiconductor (401) via an s-contact (not shown on FIG. 5B), as depictedin FIG. 4F.

Exemplary and non-limiting applications for transistor devices using thes-contact according to the various embodiments of the present disclosurecan include general analog circuits, RF switches, power amplifiers(PAs), low noise amplifiers (LNAs), analog to digital converters (ADCs),voltage controlled oscillators (VCOs), and voltage reference circuits atfrequencies ranging from DC to 100 GHz and beyond. In general, thes-contacts according to the teachings of the present disclosure can beused for any semiconductor device fabricated using CMOS technology onSOI substrate.

It should be noted that although the various exemplary embodimentsaccording to the present disclosure were provided using an exemplarycase of an N-type SOI MOSFET, such exemplary case was provided mainlyfor clarity purposes. The various embodiments of the s-contact accordingto the present invention can be equally adapted to other transistortypes and other transistor technologies, especially where the sourceand/or the drain regions extend down to an insulation layer such as a“BOX” layer of an SOI device which can prevent a conduction path forhigh energy charges during, for example, a plasma etching process.

Applications that may include the novel apparatus and systems of variousembodiments include electronic circuitry used in high-speed computers,communication and signal processing circuitry, modems, single ormulti-processor modules, single or multiple embedded processors, dataswitches, and application-specific modules, including multilayer,multi-chip modules. Such apparatus and systems may further be includedas sub-components within a variety of electronic systems, such astelevisions, cellular telephones, personal computers (e.g., laptopcomputers, desktop computers, handheld computers, tablet computers,etc.), workstations, radios, video players, audio players (e.g., mp3players), vehicles, medical devices (e.g., heart monitor, blood pressuremonitor, etc.) and others. Some embodiments may include a number ofmethods.

It may be possible to execute the activities described herein in anorder other than the order described. Various activities described withrespect to the methods identified herein can be executed in repetitive,serial, or parallel fashion.

The accompanying drawings that form a part hereof show, by way ofillustration and not of limitation, specific embodiments in which thesubject matter may be practiced. The embodiments illustrated aredescribed in sufficient detail to enable those skilled in the art topractice the teachings disclosed herein. Other embodiments may beutilized and derived there-from, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. This Detailed Description, therefore, is not to betaken in a limiting sense, and the scope of various embodiments isdefined only by the appended claims, along with the full range ofequivalents to which such claims are entitled.

Such embodiments of the inventive subject matter may be referred toherein individually or collectively by the term “invention” merely forconvenience and without intending to voluntarily limit the scope of thisapplication to any single invention or inventive concept, if more thanone is in fact disclosed. Thus, although specific embodiments have beenillustrated and described herein, any arrangement calculated to achievethe same purpose may be substituted for the specific embodiments shown.This disclosure is intended to cover any and all adaptations orvariations of various embodiments. Combinations of the aboveembodiments, and other embodiments not specifically described herein,will be apparent to those of skill in the art upon reviewing the abovedescription.

The Abstract of the present disclosure is provided to comply with 37C.F.R. §1.72(b), requiring an abstract that will allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In the foregoing DetailedDescription, various features are grouped together in a singleembodiment for the purpose of streamlining the disclosure. This methodof disclosure is not to be interpreted to require more features than areexpressly recited in each claim. Rather, inventive subject matter may befound in less than all features of a single disclosed embodiment. Thusthe following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment.

1. A device comprising: a high resistivity semiconductor substrate; atrap rich layer overlying the substrate an insulation layer overlyingthe trap rich layer; an active layer overlying the insulation layer andcomprising active regions and isolation regions of the device; atransistor formed in an isolated portion of the active layer, thetransistor comprising a drain region, a source region and a gate channelregion; and a first conductive structure resistively connecting one of:a) a drain contact or a source contact, and b) a gate contact to thesemiconductor substrate, the first conductive structure comprising: afirst conductive line connecting the one of a) and b) to a firstconductive contact, the first conductive contact extending through theactive layer at a region of the active layer outside the isolatedportion of the active layer, further extending through the insulationlayer and penetrating the trap rich layer to make resistive contact withthe semiconductor substrate.
 2. The device according to claim 1, whereinthe first conductive contact extends through the active layer at anisolation region of the device.
 3. The device according to claim 1,wherein the first conductive contact extends through the active layer atan active region of the device.
 4. The device according to claim 1,wherein an effective contact resistance between the first conductivecontact and the high resistivity semiconductor substrate is in a rangeof 0.2 to 20 G-ohm.
 5. The device according to claim 1, wherein thefirst conductive contact penetrates the trap rich layer at a depthcorresponding to a desired resistance value of the resistive contact. 6.The device according to claim 1, wherein the resistive contact with thesemiconductor region is through a thickness portion of the trap richlayer not penetrated by the first conductive contact.
 7. The deviceaccording to claim 1, wherein a resistivity value of the highresistivity substrate is in a range of 3,000 to 20,000 ohm-cm.
 8. Thedevice according to claim 1, wherein a resistivity value of the highresistivity substrate is greater than 3,000 ohm-cm.
 9. The deviceaccording to claim 1, further comprising a second conductive structurethat resistively connects the other of the one of a) and b) to thesemiconductor substrate.
 10. The device according to claim 9, whereinthe second conductive structure comprises: a second conductive lineconnecting the other of the one of a) and b) to a second conductivecontact, the second conductive contact extending through the insulationlayer and penetrating the trap rich layer to make resistive contact withthe semiconductor substrate.
 11. The device according to claim 10,further comprising one or more additional first conductive structuresand/or one or more additional second conductive structures.
 12. Thedevice according to claim 11, wherein a number of the one or moreadditional first conductive structures is based on a desired equivalentresistance between the first conductive structures and the bottomsurface of the semiconductor substrate away from the insulation layer.13. The device according to claim 12, wherein a number of the one ormore additional second conductive structures is based on a desiredequivalent resistance between the second conductive structures and thebottom surface of the semiconductor substrate away from the insulationlayer.
 14. The device according to claim 1, wherein the transistor is anN-type metal-oxide-semiconductor field effect transistor (NMOSFET). 15.The device according to claim 1, wherein the transistor is a P-typemetal-oxide-semiconductor field effect transistor (PMOSFET).
 16. Amethod for providing a discharge path to a silicon-on-insulator (SOI)transistor device, the method comprising: (i) forming an active layer ona high resistivity substrate, the active layer being isolated from thehigh resistivity substrate via an insulation layer overlying a trap richlayer formed on the high resistivity substrate; (ii) forming activeregions of the transistor device within an isolated portion of theactive layer, the active regions comprising a source region, a drainregion and a gate channel region of the transistor device; (iii) forminga first conductive structure resistively connecting at least one of: a)a drain contact or a source contact, and b) a gate contact of thetransistor device to the high resistivity substrate, the firstconducting structure being formed by: forming a first conductive lineconnecting the at least one of a) and b) to a first conductive contact;extending the first conductive contact through the active layer at aregion of the active layer outside the isolated portion of the activelayer, through the insulation layer, and penetrating the trap rich layerto make a resistive contact with the high resistivity semiconductorsubstrate, and (iv) based on the forming of the first conductivestructure, providing a first discharge path to the transistor device.17. The method according to claim 16, wherein the first conductivecontact extends through an isolation region of the active layer andstops in a region of the trap rich layer to make the resistive contactwith the high resistivity substrate.
 18. The method according to claim17, wherein the isolation region is a shallow trench isolation (STI)region.
 19. The method according to claim 16, wherein an effectivecontact resistance between the first conductive contact and the highresistivity semiconductor substrate is in a range of 0.2 to 20 G-ohm.20. The method according to claim 16, wherein a resistivity value of thehigh resistivity substrate is in a range of 3,000 to 20,000 ohm-cm.